Consolidating financial information by industry segment (Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
ASSETS:
Cash and cash equivalents	$ 2,060,524		$ 2,704,137
Reinsurance recoverables and trade receivables, net	189,498		229,343
Inventories, net	151,474		158,888
Prepaid expenses	241,711		236,915
Investments, fixed maturities and marketable equities	2,770,394		2,893,399
Investments, other	575,540		543,755
Deferred policy acquisition costs, net	152,377		103,828
Other assets	51,052		60,409
Right of use assets, financing, net	474,765		620,824
Right of use assets, operating	58,917		74,382
Related party assets	48,308		47,851
Subtotal assets	6,774,560		7,673,731
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	1,537,206		1,283,142
Buildings and improvements	7,088,810		5,974,639
Furniture and equipment	928,241		846,132
Property, plant and equipment (gross)	15,660,293		13,358,406
Less: Accumulated depreciation	(4,310,205)		(3,732,556)
Total property, plant and equipment	11,350,088		9,625,850
Total assets	18,124,648		17,299,581		$ 14,651,606
Liabilities:
Accounts payable and accrued expenses	761,039		677,785
Notes, loans and leases payable	6,108,042		6,022,497
Operating lease liabilities	58,373		74,197
Policy benefits and losses, claims and loss expenses payable	875,034		890,254
Liabilities from investment contracts	2,398,884		2,336,238
Other policyholders' funds and liabilities	8,232		10,812
Deferred income	52,282		49,157
Deferred income taxes	1,334,427		1,286,149
Related party liabilities	0		0
Total liabilities	11,596,313		11,347,089
Stockholders' equity:
Additional paid-in capital	453,643		453,819
Accumulated other comprehensive loss	(267,046)		46,384
Retained earnings	7,008,715		6,119,442
Total stockholders' equity	6,528,335		5,952,492
Total liabilities and stockholders' equity	18,124,648		17,299,581
Rental Trailers and Other Rental Equipment [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	827,696		615,679
Rental Trucks [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	5,278,340		4,638,814
Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	0		0
Amerco Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Common Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Preferred Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Operating Segments [Member] | Moving and Storage Consolidations [Member]
ASSETS:
Cash and cash equivalents	2,034,242		2,643,213
Reinsurance recoverables and trade receivables, net	107,823		142,895
Inventories, net	151,474		158,888
Prepaid expenses	241,711		236,915
Investments, fixed maturities and marketable equities	227,737		0
Investments, other	23,314		20,653
Deferred policy acquisition costs, net	0		0
Other assets	46,438		57,305
Right of use assets, financing, net	474,765		620,824
Right of use assets, operating	57,978		74,190
Related party assets	69,144		64,611
Subtotal assets	3,434,626		4,019,494
Investments in subsidiaries	450,923		737,073
Property, plant and equipment, at cost:
Land	1,537,206		1,283,142
Buildings and improvements	7,088,810		5,974,639
Furniture and equipment	928,241		846,132
Property, plant and equipment (gross)	15,660,293		13,358,406
Less: Accumulated depreciation	(4,310,205)		(3,732,556)
Total property, plant and equipment	11,350,088		9,625,850
Total assets	15,235,637		14,382,417
Liabilities:
Accounts payable and accrued expenses	729,679		663,482
Notes, loans and leases payable	6,108,042		6,022,497
Operating lease liabilities	57,418		73,998
Policy benefits and losses, claims and loss expenses payable	335,227		330,890
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	52,282		49,157
Deferred income taxes	1,405,391		1,265,430
Related party liabilities	25,082		25,668
Total liabilities	8,713,121		8,431,122
Stockholders' equity:
Additional paid-in capital	453,853		454,029
Accumulated other comprehensive loss	(272,865)		45,187
Retained earnings	7,008,505		6,119,232
Total stockholders' equity	6,522,516		5,951,295
Total liabilities and stockholders' equity	15,235,637		14,382,417
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Rental Trailers and Other Rental Equipment [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	827,696		615,679
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Rental Trucks [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	5,278,340		4,638,814
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Series A Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	0		0
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Amerco Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Common Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Operating Segments [Member] | Moving and Storage Consolidations [Member] | Preferred Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Operating Segments [Member] | Property and Casualty Insurance [Member]
ASSETS:
Cash and cash equivalents	11,276		10,800
Reinsurance recoverables and trade receivables, net	48,344		50,235
Inventories, net	0		0
Prepaid expenses	0		0
Investments, fixed maturities and marketable equities	271,156		297,488
Investments, other	125,130		114,269
Deferred policy acquisition costs, net	0		0
Other assets	730		371
Right of use assets, financing, net	0		0
Right of use assets, operating	914		93
Related party assets	2,347		6,713
Subtotal assets	459,897		479,969
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	0		0
Property, plant and equipment (gross)	0		0
Less: Accumulated depreciation	0		0
Total property, plant and equipment	0		0
Total assets	459,897		479,969
Liabilities:
Accounts payable and accrued expenses	4,470		3,849
Notes, loans and leases payable	0		0
Operating lease liabilities	928		93
Policy benefits and losses, claims and loss expenses payable	153,007	$ 153,007	160,379	$ 160,379
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	2,702		3,521
Deferred income	0		0
Deferred income taxes	1,713		12,803
Related party liabilities	2,544		3,196
Total liabilities	165,364		183,841
Stockholders' equity:
Additional paid-in capital	91,120		91,120
Accumulated other comprehensive loss	(14,720)		16,630
Retained earnings	214,832		185,077
Total stockholders' equity	294,533		296,128
Total liabilities and stockholders' equity	459,897		479,969
Operating Segments [Member] | Property and Casualty Insurance [Member] | Rental Trailers and Other Rental Equipment [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Rental Trucks [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Series A Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Amerco Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	3,301		3,301
Operating Segments [Member] | Property and Casualty Insurance [Member] | Common Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	0		0
Operating Segments [Member] | Property and Casualty Insurance [Member] | Preferred Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	0		0
Operating Segments [Member] | Life Insurance [Member]
ASSETS:
Cash and cash equivalents	15,006		50,124
Reinsurance recoverables and trade receivables, net	33,331		36,213
Inventories, net	0		0
Prepaid expenses	0		0
Investments, fixed maturities and marketable equities	2,271,501		2,595,911
Investments, other	427,096		408,833
Deferred policy acquisition costs, net	152,377		103,828
Other assets	3,884		2,733
Right of use assets, financing, net	0		0
Right of use assets, operating	25		99
Related party assets	12,268		16,911
Subtotal assets	2,915,488		3,214,652
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	0		0
Property, plant and equipment (gross)	0		0
Less: Accumulated depreciation	0		0
Total property, plant and equipment	0		0
Total assets	2,915,488		3,214,652
Liabilities:
Accounts payable and accrued expenses	26,890		10,454
Notes, loans and leases payable	0		0
Operating lease liabilities	27		106
Policy benefits and losses, claims and loss expenses payable	386,800		398,985
Liabilities from investment contracts	2,398,884		2,336,238
Other policyholders' funds and liabilities	5,530		7,291
Deferred income	0		0
Deferred income taxes	(72,677)		7,916
Related party liabilities	13,644		12,717
Total liabilities	2,759,098		2,773,707
Stockholders' equity:
Additional paid-in capital	26,271		26,271
Accumulated other comprehensive loss	(207,327)		87,200
Retained earnings	334,946		324,974
Total stockholders' equity	156,390		440,945
Total liabilities and stockholders' equity	2,915,488		3,214,652
Operating Segments [Member] | Life Insurance [Member] | Rental Trailers and Other Rental Equipment [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Operating Segments [Member] | Life Insurance [Member] | Rental Trucks [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Operating Segments [Member] | Life Insurance [Member] | Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Life Insurance [Member] | Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Operating Segments [Member] | Life Insurance [Member] | Series A Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	0		0
Operating Segments [Member] | Life Insurance [Member] | Amerco Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	2,500		2,500
Operating Segments [Member] | Life Insurance [Member] | Common Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	0		0
Operating Segments [Member] | Life Insurance [Member] | Preferred Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	0		0
Eliminations [Member]
ASSETS:
Cash and cash equivalents	0		0
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	0		0
Investments, fixed maturities and marketable equities	0		0
Investments, other	0		0
Deferred policy acquisition costs, net	0		0
Other assets	0		0
Right of use assets, financing, net	0		0
Right of use assets, operating	0		0
Related party assets	(35,451)		(40,384)
Subtotal assets	(35,451)		(40,384)
Investments in subsidiaries	(450,923)		(737,073)
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	0		0
Property, plant and equipment (gross)	0		0
Less: Accumulated depreciation	0		0
Total property, plant and equipment	0		0
Total assets	(486,374)		(777,457)
Liabilities:
Accounts payable and accrued expenses	0		0
Notes, loans and leases payable	0		0
Operating lease liabilities	0		0
Policy benefits and losses, claims and loss expenses payable	0		0
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	0		0
Deferred income taxes	0		0
Related party liabilities	(41,270)		(41,581)
Total liabilities	(41,270)		(41,581)
Stockholders' equity:
Additional paid-in capital	(117,601)		(117,601)
Accumulated other comprehensive loss	227,866		(102,633)
Retained earnings	(549,568)		(509,841)
Total stockholders' equity	(445,104)		(735,876)
Total liabilities and stockholders' equity	(486,374)		(777,457)
Eliminations [Member] | Rental Trailers and Other Rental Equipment [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations [Member] | Rental Trucks [Member]
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations [Member] | Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations [Member] | Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations [Member] | Series A Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	0		0
Eliminations [Member] | Amerco Common Stock [Member]
Stockholders' equity:
Common stock, value, issued	(5,801)		(5,801)
Eliminations [Member] | Common Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	0		0
Eliminations [Member] | Preferred Stock in Treasury [Member]
Stockholders' equity:
Treasury stock, value	$ 0		$ 0